Electrochemical determination of the permeability of porcine mucus to model solute compounds

An electrochemical approach to the determination of permeability through native mucus gel of simple electrochemically active solutes is reported. For all the solutes studied, a reduction in effective diffusion coefficients was observed, with retardation of solute flux by a factor of at least two. However, NADH and the dicarboxylic acid derivative of ferrocene demonstrated a substantial, almost ten-fold, reduction in permeability through mucus. Results for the controls were in reasonable agreement with literature values where available. No consistent effect of molecular weight was evident with regard to the barrier properties of mucus over the molecular weight range of solutes investigated (34-660 daltons). The results suggest that mucus is acting more than as a gel support for an unstirred water layer.